Equalization of Frequency-Dependent Gain

ABSTRACT

Systems, devices, and methods for determining and establishing frequency-dependent gain compensation in wide bandwidth communication systems are disclosed. Variable frequency-dependent gain compensation circuits, or variable equalizers, have settings that configure them to establish discrete frequency-dependent gain compensation. The frequency-dependent gain compensation can include various types and levels of gain slope and/or ripple. The settings of the variable equalizers can be set by control signals established a control circuit in response to signals from an external computer. The variable equalizers are coupled to other circuits or devices and the frequency-dependent gain of the combined circuit are measured. The settings of the variable equalizer are then changed to establish an optimal frequency-dependent gain profile or frequency-dependent gain that is closest to a predetermined frequency-dependent target gain profile. The settings can then be saved in a memory or register.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/941,023 filed 18 Feb. 2014, entitled Equalization ofFrequency-Dependent Gain, which is incorporated by reference herein.

BACKGROUND

The present disclosure is generally related to wireless communication,and in particular, to frequency-dependent gain compensation in microwaveand radio frequency transmitters and receivers.

Unless otherwise indicated herein, the approaches described in thissection are not admitted to be prior art by inclusion in this section.

Satellite-based and other wireless communication systems can be used todeploy communication network access to areas without the terrestrialinfrastructure to support other forms of network connectivity (e.g.,telephone or DSL lines, cable lines, fiber optic lines, etc.). Forexample, satellite networks can be deployed to provide internet accessto wide regions of users that are either mobile or too remote for wiredconnections to be feasible. Similarly, point-to-point wireless datacommunication systems (e.g., microwave transceiver networks) can be usedto connect computer networks of two or more geographically separatedfacilities to enable increased connectivity and data sharing betweencomputer systems and users in those networks.

Connections using wireless communication systems can be deployed morequickly and, in some instances, at lower costs relative to installingtraditional wired or fiber optic connections. However, due to thebandwidth limitations and latency issues of traditional wirelessconnections relative to the wide bandwidth capabilities of wired orfiber optic connections, wireless systems have often been used asconnections of last resort. For instance, users in remote areastypically have limited options. Such users may have access totraditional telephone and dial-up data services over a public switchedtelephone network (PSTN). But because PSTNs may have limited quality andreliability in such remote areas, many remote users may resort tosatellite-based wireless connections for data or Internet access.Traditionally, such satellite-based wireless connections have offeredonly marginal performance improvements over dial-up type services, butwith the advantages of improved reliability (i.e., availability anduptime). However, such advantages can be costly.

Since each location's hardware (e.g., modem, transceiver, antenna, etc.)must be installed and aligned individually, the cost of installation,especially in remote areas, may be significant. In addition, because ofthe small user base and traditionally narrow bandwidths, conventionalsatellite communications systems have yet to achieve economies of scale.Consequently, installation and subscription costs for satellite basedwireless connections can be prohibitive for many casual users.

Recently, the speed and bandwidth of various satellite-based and otherwireless connections have increased significantly. Satellite systemswith increased bandwidths, improved spot beam handling, and frequencyreuse, have improved the data capacity and the speed of satellitecommunication to the point that some systems are now competitive withtraditional wired high speed connections in terms of both cost andperformance.

SUMMARY

Embodiments of the present disclosure include systems, methods, anddevices for improved frequency-dependent gain compensation in wirelesscommunication. One embodiment includes a variable gain compensationcircuit to establish a variable frequency-dependent gain, and a controlcircuit that includes an input terminal and is coupled to the variablegain compensation circuit. The control circuit can be configured tocontrol the variable frequency-dependent gain of the variable gaincompensation circuit in response to a signal received on the inputterminal from an external source.

In one embodiment, the control circuit further comprises a register. Thecontrol circuit establishes a control signal to control the variablefrequency-dependent gain of the variable gain compensation circuit inaccordance with a predetermined setting stored in the register.

In one embodiment, the variable gain compensation circuit comprises aplurality of N variable gain compensation devices to establish aplurality of N corresponding component variable frequency-dependentgains. The variable frequency-dependent gain of the variable gaincompensation circuit is a composite of at least some of the plurality ofthe N component variable frequency-dependent gains.

In one embodiment, the plurality of N variable gain compensation devicesare the same and the corresponding plurality of N component variablefrequency-dependent gains are approximately equal to each other.

In one embodiment, at least one of the plurality of N variable gaincompensation devices is different from at least one other of theplurality of N variable gain compensation devices, and wherein at leastone of the corresponding plurality of N component variablefrequency-dependent gains is different from at least one other of theplurality of N component variable frequency-dependent gains.

In one embodiment, the variable gain compensation circuit comprises aplurality of M possible configurations to establish a plurality of Mcorresponding discrete frequency-dependent gains.

Another embodiment includes a transceiver circuit that includes atransmit path comprising a first variable gain compensation circuit toestablish a variable frequency-dependent transmit gain, a receive pathcomprising a second variable gain compensation circuit to establish avariable frequency-dependent receive gain, and a control circuitcomprising an input terminal coupled to the first variable gaincompensation circuit and the second variable gain compensation circuit.The control circuit can be configured to control the variablefrequency-dependent transmit gain of the first variable gaincompensation circuit and the variable frequency-dependent receive gainof the second variable gain compensation circuit in response to a signalreceived on the input terminal from an external source.

In some embodiments, the transmit path includes a first plurality ofsignal processing devices, wherein the variable frequency-dependenttransmit gain of the first variable gain compensation circuit is set inresponse to a first frequency-dependent gain of the first plurality ofsignal processing devices. In some embodiments, the receive pathincludes a second plurality of signal processing devices, wherein thevariable frequency-dependent receive gain of the second variable gaincompensation circuit is set in response to a second frequency-dependentgain of the second plurality of signal processing devices.

Yet another embodiment includes a method of equalizingfrequency-dependent gains in an integrated circuit comprising. Themethod can include providing a plurality of signal processing devices,defining a transmit path through a first subset of the plurality ofsignal processing devices, defining a receive path through a secondsubset of the plurality of signal processing devices, coupling a firstvariable gain compensation circuit to the transmit path, and coupling asecond variable gain compensation circuit to the receive path.

In one embodiment, the method can also determining a firstfrequency-dependent gain through the transmit path, determining a secondfrequency-dependent gain through the receive path, configuring the firstvariable gain compensation circuit in response to the firstfrequency-dependent gain of the transmit path to establish acompensating frequency-dependent transmit gain, and configuring thesecond variable gain compensation circuit in response to the secondfrequency-dependent gain of the receive path to establish a compensatingfrequency-dependent receive gain.

In one embodiment, configuring the first variable gain compensationcircuit comprises selecting one of a plurality of M discrete settingsfor the first variable gain compensation circuit, and whereinconfiguring the second variable gain compensation circuit comprisesselecting one of a plurality of N discrete settings for the secondvariable gain compensation circuit.

The following detailed description and accompanying drawings provide abetter understanding of the nature and advantages of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a communication device according to variousembodiments of the present disclosure.

FIG. 2 is a schematic of a transmit receive integrated assembly (TRIA)that can be improved by various embodiments of the present disclosure.

FIG. 3 is an example graph of a frequency-dependent gain profile withnegative gain slope.

FIG. 4 is an example graph of a frequency-dependent gain profile withpositive gain slope.

FIG. 5 is a schematic of a transceiver module with gain compensationaccording to various embodiments of the present disclosure.

FIG. 6 is an example graph of variable frequency-dependent gaincompensation that can be established by various embodiments of thepresent disclosure.

FIG. 7 is a schematic of a variable equalizer according to variousembodiments of the present disclosure.

FIG. 8 is an example graph of variable frequency-dependent gaincompensation that can be established by various embodiments of thepresent disclosure.

FIG. 9 is a schematic of a system for establishing variablefrequency-dependent gain using a variable equalizer according to variousembodiments of the present disclosure.

FIG. 10 is a schematic of a signal processing device with variablefrequency-dependent gain compensation according to various embodimentsof the present disclosure.

FIG. 11 is a flowchart of a method according to one embodiment of thepresent disclosure.

FIG. 12 illustrates a computer system that can use and be used toimplement embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure pertains to wireless and satellite communicationdevices, methods, and systems, and in particular to techniques forequalizing frequency-dependent gain in signal processing devices, suchas transceivers and transmit/receive integrated assemblies (TRIAs).Reference will now be made to the exemplary embodiments illustrated inthe drawings, and specific language will be used herein to describe thesame. It will nevertheless be understood that no limitation of the scopeof the invention is thereby intended. Alterations and furthermodifications of the inventive features illustrated herein, andadditional applications of the principles of the inventions asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the invention.

In describing the present disclosure, the following terminology will beused: The singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to an item includes reference to one or more items. The term“ones” refers to one, two, or more, and generally applies to theselection of some or all of a quantity. The term “plurality” refers totwo or more of an item. The term “device” may refer to one functionalunit, which may include one or multiple functional sub-units. The term“about” means quantities, dimensions, sizes, formulations, parameters,shapes and other characteristics need not be exact, but may beapproximated and/or larger or smaller, as desired, reflecting acceptabletolerances, conversion factors, rounding off, measurement error and thelike and other factors known to those of skill in the art. The term“substantially” means that the recited characteristic, parameter, orvalue need not be achieved exactly, but that deviations or variations,including for example, tolerances, measurement error, measurementaccuracy limitations and other factors known to those of skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide. Numerical data may be expressedor presented herein in a range format. It is to be understood that sucha range format is used merely for convenience and brevity and thusshould be interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also interpreted toinclude all of the individual numerical values or sub-ranges encompassedwithin that range as if each numerical value and sub-range is explicitlyrecited. As an illustration, a numerical range of “about 1 to 5” shouldbe interpreted to include not only the explicitly recited values ofabout 1 to about 5, but also to include individual values and sub-rangeswithin the indicated range. Thus, included in this numerical range areindividual values such as 2, 3 and 4 and sub-ranges such as 1-3, 2-4 and3-5, etc. This same principle applies to ranges reciting only onenumerical value (e.g., “greater than about 1”) and should applyregardless of the breadth of the range or the characteristics beingdescribed. A plurality of items may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. Furthermore, where the terms “and” and “or” are used inconjunction with a list of items, they are to be interpreted broadly, inthat any one or more of the listed items may be used alone or incombination with other listed items. As used in this application, theterm “or” is intended to mean an inclusive “or” rather than an exclusive“or”. That is, unless specified otherwise, or clear from context, “Xincludes A or B” is intended to mean any of the natural inclusivepermutations. That is, if X includes A; X includes B; or X includes bothA and B, then “X employs A or B” is satisfied under any of the foregoinginstances. The term “alternatively” refers to selection of one of two ormore alternatives, and is not intended to limit the selection to onlythose listed alternatives or to only one of the listed alternatives at atime, unless the context clearly indicates otherwise.

Overview

Embodiments of the present disclosure include systems, devices, andmethods for compensating for frequency-dependent gain in electronicdevices. One example embodiment includes a variable frequency-dependentgain compensation circuit. The variable frequency-dependent gaincompensation circuit can be set to establish a particularfrequency-dependent gain to compensate for frequency-dependent gain ofother components and devices to which it is coupled. For example, avariable frequency-dependent gain compensation circuit can be coupled toand set to compensate for the frequency-dependent gain in a particularsignal processing circuit or device (e.g., a transceiver module). In oneembodiment, one or more variable frequency-dependent gain circuits canbe implemented in an integrated circuit (IC). In another embodiment, oneor more variable frequency-dependent gain circuits can be implemented inmonolithic microwave integrated circuit (MMIC). As used herein,implementing a circuit in a particular form factor can includefabricating the circuit (i.e., fabricating the circuit as an IC orMMIC). Such integrated circuits can be coupled to other components in aparticular device and set to compensate for the frequency-dependent gainof the components in the device.

In one example embodiment, a particular signal processing device (e.g.,a transmitter, a receiver, a transceiver, a TRIA, etc.) may include anumber of different signal processing components, such as frequencyconversion circuits, amplifiers, and the like, each with its ownfrequency-dependent gain. The combination of the frequency-dependentgains of the components can result in a frequency-dependent gain. Thecharacteristics of the frequency-dependent gain may not be ideal oracceptable for a particular purpose.

For instance, for transmission of wireless communication signals inmicrowave and RF frequencies, frequency-dependent gain with excessivegain slope or ripple requires increased dynamic range in the signal toavoid clipping the signals in the frequencies with more gain and losingthe signals in the noise in the frequencies with less gain. Increasingthe dynamic range of a particular system may be undesirable or untenablefor various reasons. For example, the additional power required forboosting the dynamic range may be impossible, or at least unsustainable,given the type or amount of available power (e.g., a solar or batterypowered system). Accordingly, variable frequency-dependent gaincompensation circuits can be set to have complementaryfrequency-dependent gain to adjust the frequency-dependent gain of thedevice to an acceptable uniformity or flatness. In some embodiments,acceptable uniformity or flatness may be defined as a total range ofgain from maximum gain to minimum gain (e.g., a range of 4 dB frommaximum to minimum).

In one embodiment, the variable frequency-dependent gain circuit coupledto a particular device or circuit can be set to establish a compositefrequency-dependent gain that is substantially flatter (i.e., less steepgain slope or smaller gain ripple) than the frequency-dependent gain ofthe components in the particular device or circuit without the variablefrequency-dependent gain circuit. When the composite frequency-dependentgain of the system is flatter, then the dynamic range can be improved,providing various performance benefits. On the transmission side,improved dynamic range can help reduce power consumption. For example,improvements to the dynamic range in a receiver or a receive path of acircuit resulting from flatter gain response increases its efficacy whenreceiving and processing weaker signals. Weaker signals can be detectedand differentiated even in the presence of much stronger signals atnearby frequencies without the need for RF filtering, which can belarge, expensive, or impractical (i.e., the nearby frequencies may betoo close to the desired signal to filter effectively in the RF domain).In addition, improved dynamic range may also allow for signals atadjacent frequency bands to be down-converted without distortion. Theundistorted down-converted signals can then be sampled, digitallyfiltered, and processed. Improved dynamic range can also preventintentional or unintentional jamming from interference sources at nearbyfrequencies since the receiver is able to process both largeinterference signals and small desired signals at the same time withless distortion. Improved dynamic range can also result in lowerdistortion from adjacent carriers of similar signal strength which canimprove the effective signal to noise and interference ratio.

In one embodiment, the variable frequency-dependent gain circuit can becontrolled by an external source (e.g., a testing computer) toiteratively determine the optimal settings given the frequency-dependentgain of the particular device or circuit to which it is coupled. Inother embodiments, the optimal settings for the variablefrequency-dependent gain circuit can be stored in a register, or othermemory, and used to set the variable frequency-dependent gain of thevariable frequency-dependent gain circuit.

These and other embodiments of the present disclosure are described inmore detail below.

Wireless Communication Systems and Devices

FIG. 1 illustrates a wireless communication system 100 that can beimproved by various embodiments of the present disclosure. The wirelesscommunication system 100 may be deployed at both end user locations andservice provider locations. As shown, the wireless communication system100 may be implemented as a two-part indoor/outdoor system. For example,the indoor unit 105 may be installed in the interior of an end user'sbuilding and connected to various other electronic devices that use thewireless communication system 100 to exchange signals with a remotewireless communication partners. The outdoor unit 110 may be installedon the exterior of the building (e.g., on a rooftop, or side of thebuilding) with line of sight or unobstructed views of remote wirelesscommunication partners, such as satellite 101, wireless access point102, and the like.

The indoor unit 105 may include a modem, and other components, that canbe connected to a router or computing device using one or more networkcommunication protocols or media (e.g., Ethernet, Wi-Fi, etc.). Theoutdoor unit 110 may include the components for transmitting/receivingelectromagnetic signals at various frequencies. Thetransmitting/receiving components may include transmission devices andreceiving devices used in combination with an antenna 140. In theparticular example shown, the transmitting/receiving components inoutdoor unit 110 may include a transmit-receive integrated assembly(TRIA) 120. The TRIA 120 may include electronic components forming atransmission path coupled to one or more transmission antenna elements,and electronic components forming a receive path coupled to one or morereceive antenna elements. The transmission antenna elements and thereceive path antenna elements may be coupled to one or more types ofopen-ended waveguide type antennas 130, such as horn antennas. Whencombined with a reflector antenna 140, the TRIA 120 and antenna 130combination can be configured to send and receive electronic signalsto/from discrete locations over particular angles of transmission andacceptance. For example, the outdoor unit 110 may be aimed at particularsource or target, such as a geostationary satellite 101 or terrestrialaccess point 102, to send/receive signals exclusively to/from thattarget or source.

In such configurations, the indoor unit 105 and the outdoor unit 110 maybe coupled to one another by connection 115. In one embodiment, theconnection 115 may include a flexible waveguide such as coaxial cable ora twisted-pair cable (e.g., CAT5 cable). In some embodiments, theconnection 115 may also include power transmission capabilities forproviding electrical power to the outdoor unit 110. For example, theconnection 115 may include a CAT5 cable configured to deliver power overEthernet.

FIG. 2 illustrates a particular example implementation of a TRIA 120 toillustrate various components that can contribute to thefrequency-dependent gain of a system or device as a whole. The TRIA 120may include a terminal 117 coupled to indoor unit 110 through theconnection 115. Signals received on terminal 117 can be processed by thevarious components of the TRIA 120 and output on transmission terminal118 and one or more transmission antenna elements 135-1. The TRIA 120may also include a receive terminal 119 coupled to one or more receiveantenna elements 135-2. Electromagnetic signals received through thereceive terminal 119 via one or more receive antenna elements 135-2 canbe processed by the various components of the TRIA 120 and output onterminal 117 and sent to the indoor unit 105 over connection 115.

The TRIA may include any number of components, such as signal processingcircuits, power conditioning circuits, memories, control circuits, andthe like. As shown, the TRIA 120 can include a modulator 121, a tuner122, and a transceiver module 123. The transceiver module 123 mayinclude a transmission path 132 and a receive path 133. Transmissionpath 132 of the transceiver module 123 may be coupled to a poweramplifier 124. In one particular embodiment, the power amplifier 124 mayinclude component amplifier modules 125-1 and 125-2. The componentamplifier module 125-1 may include a gallium arsenide (GaAs)application-specific integrated circuit (ASIC) amplifier, while thecomponent amplifier module 125-2 may include a gallium nitride (GaN)ASIC amplifier. The receive path 133 of the transceiver module 123 maybe coupled to one or more low noise amplifiers (LNAs) 127. In someembodiments, the receive antenna element 135-2 may include multipleantennas for receiving signals having various polarizations. In suchembodiments, each polarization may include its own set of LNAs 127 andcorresponding receive paths 133.

Signals received on the input 117 by the TRIA 120 from the indoor unit110 can be fed into modulator 121. Modulator 121 can generate amodulated signal on one or more carrier signals with the receivedsignals. The received signals may include analog and/or digital signals.The modulated signal can then be fed into the tuner 122 to convert themodulated signal to the desired frequency used by the transceiver module123. In the particular example shown, the tuner 122 can convert themodulated signal into an S band signal. The transceiver module 123 canreceive the transmission signal on an input of its transmission path132. The transmission path 132 can process the transmission signalaccording to the requirements of the specific application in which theTRIA 120 is implemented. For example, the transmission path 132 caninclude a number of signal conversion device or circuits to convert theinput signal from one frequency to another frequency. In this particularexample, the transmission path 132 of the transceiver module 123converts the transmission signal from S band frequencies toapproximately 7 GHz. The transmission path 132 may also include a numberof amplifiers and/or conditioning circuits to amplify and/or conditionthe converted transmission signal. The converted transmission signal canthen be fed into the power amplifier 124. The power amplifier 124 canamplify the converted transmission signal and output the amplifiedsignal on output terminal 118 coupled to transmission antenna element135-1.

On the receive side of the TRIA 120, electromagnetic signals received onterminal 119 through receive antenna element 135-2 can be amplified andfiltered using the various LNAs 127. The amplified received signals canbe fed into the receive path 133 of the transceiver module 123 toprocess the received signal according to the requirements of thespecific application in which the TRIA 120 is implemented. The receivepath 133 may include a number of signal conversion devices or circuitsto convert the received signal from one frequency to another. Forexample, the receive path 133 can convert the received 7 GHz signal intoan 800 MHz signal (UHF). Similar to the transmission path 132, thereceive path 133 may also include a number of amplifiers and/orconditioning circuits to amplify and/or condition the received signal.The converted received signal can then be fed into the tuner 122 and themodulator 121 to convert signal into a format that can be used by theindoor unit 110.

Each of various components of the TRIA 120 may have a particularfrequency-dependent response to a given transmission or receive signal.For the sake of clarity and brevity, the term “signal” will be used torefer to any transmission or receive signal processed by one of thecomponents of the TRIA 120. Such signals may include various frequenciesand/or frequency bands in a particular bandwidth of frequencies. As anyone or more of the components of the TRIA 120 process signals at variousfrequencies, the signal may be either amplified or attenuated based onthe response of the components to the particular frequencies in thesignal. This response is referred to herein as “frequency-dependentgain”. Based on the frequency-dependent gain of each component deviceand circuit, the TRIA 120, or other device, can have afrequency-dependent gain that includes the frequency-dependent gaincontributions of the components devices and circuits. Accordingly, thetransmission path 132 may have one frequency-dependent gain profile,while the receive path 133 133 may have a different frequency-dependentgain profile. The frequency-dependent gain profile of either path can bedetermined by measuring the frequency-dependent gain between theterminals 131-1, 131-2 and/or 131-3 of the TRIA 120. Accordingly, thefrequency-dependent gain for the transmission path 132 and the receivepath 133 can be determined independently.

In general, gain can be measured in decibels (dB) relative to the inputsignal. Circuits and devices establish different levels of gain fordifferent signal frequencies. As such, circuits and devices that areused to process or otherwise handle variable frequency or wide bandwidthsignals may have corresponding frequency-dependent gains. Accordingly,the frequency-dependent gain for a particular circuit or device can beplotted in decibels over a range of frequencies. The resulting graph isreferred to herein as a “frequency-dependent gain profile”. FIG. 3illustrates an example frequency-dependent gain profile.

Frequency-Dependent Gain and Frequency-Dependent Gain Profiles

As shown in FIG. 3, the frequency-dependent gain profile 300 is measuredover some range of frequencies and has a range of gain values 315 (e.g.,L dB) ranging from a minimum gain value 305 to the maximum gain value310. The particular example frequency-dependent gain profile 300illustrates a drop-off in gain as a function of frequency. Thischaracteristic of a frequency-dependent gain profile is referred toherein as the “negative gain slope”. While it is possible for thefrequency-dependent gain profile to be linear, the example shown in FIG.3 illustrates how the negative gain slope of the frequency-dependentgain represented by the frequency-dependent gain profile 300 of aparticular circuit or device may be nonlinear. The nonlinearity of thefrequency-dependent gain may be represented by one or more curves in thefrequency-dependent gain profile. In the example shown in FIG. 3, thenonlinearity of the frequency-dependent gain is illustrated as a slightdownward curve in the frequency-dependent gain profile 300.

FIG. 4 illustrates a frequency-dependent gain profile 400 of anotherparticular circuit or device with a “positive gain slope”. In thisexample, the gain increases from the minimum gain 405 to the maximumgain 410 as the frequency increases. Not only is the sign of the gainslope of frequency-dependent gain profile 400 the opposite of the signof the gain slope of the frequency-dependent gain profile 300, the rangeof gain 415 (X db), given that the scale of the gain axes are the same,is smaller than the range of gain 315 (L db), such that L>X.Frequency-dependent gain profiles having gain slope with smaller rangesof gains and/or smaller slopes are referred to herein as having “flattergain slope” than frequency-dependent gain profiles having gain slopeswith larger ranges of gain and/or steeper slopes. Accordingly,frequency-dependent gain profile 400 may be considered flatter than thefrequency-dependent gain profile 300.

The nonlinearity of the frequency-dependent gain may be represented byone or more curves in the frequency-dependent gain profile.Frequency-dependent gain profiles 300 and 400 are monotonic and eachincludes a single curve. However, it is possible for circuits anddevices to have nonlinear frequency-dependent gains that can berepresented by frequency-dependent gain profiles that are non-monotonicand have both positive and negative slopes. For example, somefrequency-dependent gain profiles can be approximated by higher orderpolynomials. When a frequency-dependent gain profile is non-monotonicover some region of the frequency band, the frequency-dependent gain issaid to have “gain ripple”. The smaller the amplitude of the gainripples, the flatter the frequency-dependent gain profile is considered.Accordingly, a frequency-dependent gain profile with shallow slope andlow amplitude ripple is said to be flatter than a frequency-dependentgain profile with a steep slope and a higher amplitude ripple.

In many instances, a flat frequency-dependent gain is desirable. Inparticular, in wireless communication systems, because every componentfrequency of a given signal is amplified or attenuated according to thefrequency-dependent gain of a particular circuit or device, circuits ordevices with larger ranges of gain may suffer from various limitations.In particular, when transmitting electromagnetic signals over widebandwidths, systems with significant gain slope or high amplitude gainripple may cause some portions of the signal transmitted or receivedwith a given power to be clipped or lost in the noise. To counteractthis effect, the entire system may be operated with higher dynamicallyranges. The drawback to operating the communication system with higherdynamic ranges is an increase in power consumption. According to variousembodiments of the present disclosure, to avoid operating a giventransceiver with unnecessary dynamic range, the frequency-dependent gainof a given system can be compensated by using one or more variablefrequency-dependent gain compensation circuits. In the interest ofclarity and brevity variable frequency-dependent gain compensationcircuits are also referred to herein as “variable equalizers”.

Variable Frequency-Dependent Gain Compensation Circuits and Equalizers

FIG. 5 illustrates an embodiment of the present invention in whichmultiple variable equalizers 510 can be included in the transmission andreceive paths 132 and 133 of transceiver circuit module 123. As shown,the transmission path 132 from transmission input 520 to transmissionoutput 525 can be equalized separately from the receive path 133 fromreceive input 570 to receive output 575. In the particular exampleshown, the transmission path 132 includes a number of signal processingcomponents 530 coupled to the input terminals and the output terminalsof the variable equalizers 510. The signal processing components 530 mayinclude a number of amplifiers, signal frequency converters and/ormixers. Similarly, the receive path 133 can include a number of signalprocessing components 540. The receive signal processing components 540can include a number of amplifiers, signal frequency converters, and/ormixers. While not shown, the transceiver circuit module 123 can alsoinclude a control circuit to establish control signals to control thevariable equalizers 510. In such embodiments, the control circuit canestablish control signals in response to stored predetermined settingsor signals received from an external source.

Variable equalizers 510 can be coupled to one or more of the varioussignal processing components 530 and 540. While one particular exampleconfiguration of circuitry of the transceiver module 123 according toone embodiment is shown in FIG. 5, one of ordinary skill in the art willrecognize other configurations of signal processing components 530 and540 and variable equalizers 510 are possible without departing from thespirit or scope of the present disclosure. In one embodiment, thevariable equalizers 510 may be substantially the same as the othervariable equalizers 510. Accordingly, the design of the components andcircuitry of variable equalizers 510 may be substantially similar, ifnot identical, such that the level and type of variablefrequency-dependent gains that each variable equalizer 510 can establishwill be substantially similar, if not identical.

In other embodiments, the variable equalizers 510 can each have adifferent design and/or configuration of internal circuitry andcomponents, such that the level and type of variable frequency-dependentgains established by each of the variable equalizers 510 will bedifferent. Embodiments in which the equalizers 510 are the same anddifferent are associated with various advantages and drawbacks. Forexample, in embodiments which the equalizers 510 are the same thecomplexity of setting each of the variable equalizers 510 may be reducedgiven that only fixed number of potential gain compensation profiles maybe achieved. In contrast, in other embodiments in which the equalizers510 are different or varied, the gain compensation that can be achievedcan be more customized to a greater degree according to thefrequency-dependent gain profile of the circuits or devices to which theequalizers 510 or coupled.

FIG. 6 illustrates a graph 600 of M discrete frequency-dependent gainprofiles corresponding to the M discrete possible frequency-dependentgains possible with M settings of a particular equalizer 510, inaccordance with embodiments of the present disclosure. In oneembodiment, particular variable equalizers 510 may be configurable toestablish some fixed number of discrete frequency-dependent gains. Inthe example shown in FIG. 6, the variable equalizer 510 may be set toestablish M, wherein M=3, frequency-dependent gains corresponding tofrequency-dependent gain profiles 610, 620, and 630. Frequency-dependentgain profile 610 indicates that the corresponding frequency-dependentgain of the variable equalizer 510 is set to include a negative gainslope. Frequency-dependent gain profile 620 indicates that thecorresponding frequency-dependent gain of the variable equalizer 510 isset to be flat across all frequencies (i.e., no gain slope or ripple).Finally, the frequency-dependent gain profile 630 indicates that thecorresponding frequency-dependent gain of the variable equalizer 510 isset to include a positive gain slope.

Depending on the particular configuration and components of the variableequalizer 510, the available frequency-dependent gains may besubstantially linear for various portions of the frequency spectrum. Forexample, as illustrated in FIG. 6, the frequency-dependent gain profiles610, 620, and 630 are all substantially linear within range 645 betweenlower frequency 640-1 and upper frequency 640-2. Accordingly, theconfiguration and components of the variable equalizer 510 can be chosenso that the possible gains established are linear across a particularrange 645 interest. Accordingly, the size and placement of range 645 maybe adjusted up or down in order to better compensate forfrequency-dependent gain slope and ripple due to other components of thetransceiver module 123 or the TRIA 120, according to various embodimentsof the present disclosure.

Variable Equalizers

FIG. 7 illustrates an example variable equalizer 510A according tovarious embodiments of the present disclosure. As shown, the variableequalizer 510A can include an input terminal 518 and output terminal519. An amplifier 514 can be coupled to the input terminal 518 and theoutput terminal 518. In one embodiment, a number of electroniccomponents can be selectively coupled in parallel to the amplifier 114.In the example shown, conductor 511, capacitor 512, and/or resistor 513may be coupled to the amplifier 514 in parallel selectively by switches515, 516 and 517, respectively. Accordingly, the amplifier 514 may beprovided feedback through any one or more of inductor 511, capacitor512, and/or resistor 513 to establish frequency-dependent gain withpositive, negative, or zero gain slope. The magnitude and sign of theslope can depend on the particular values chosen for each one of thecomponents 511, 512, and 513 as well as the type of amplifier chosen foramplifier 514.

For example, when only the switches 515 are closed to couple theinductor 511 to the amplifier 540 in parallel, the frequency-dependentgain of the variable equalizer 510A will have a positive gain slope.This is illustrated in FIG. 6 by frequency-dependent gain profile 630.When only switches 516 are close to couple the capacitor 512 to theamplifier 514 in parallel, the frequency-dependent gain of the variableequalizer 510A will have a negative gain slope. This is illustrated inFIG. 6 by frequency-dependent gain profile 610. Additionally, when onlyswitches 517 are closed to couple the resistor 513 to amplifier 514 inparallel, the frequency-dependent gain of the variable equalizer 510Awill have zero gain slope, as illustrated by frequency-dependent gainslope profile 620 in FIG. 6. While the frequency-dependent gain profiles610 and 630 are illustrated as being symmetrical about theirintersection point with the frequency-dependent gain profile 620, insome embodiments the frequency-dependent gain profiles 610 and 630 arenot symmetrical. Accordingly, in variable equalizers 510 that have somenumber M of possible asymmetrical frequency-dependent gains, thecorresponding frequency-dependent gain profiles may intersect each otherat multiple frequencies. For example, frequency-dependent gain profile630 may be shifted up so that it intersects the frequency-dependent gainprofile 620 at a frequency greater than the frequency at whichfrequency-dependent gain profiles 610 and 620 intersect.

As mentioned above, each set of switches 515, 516, and 517 can beoperated independently to couple one or more of inductor 511, capacitor512, and resistor 513 to the amplifier 514 alone or in combination withone another to establish a desired frequency-dependent gain. In oneembodiment, the frequency-dependent gain of the variable equalizer 510can be set to compensate for the frequency-dependent gain of othercomponents to which the variable equalizer 510 is coupled. For example,if an amplifier 530-1, signal mixer/converter 530-2, and/or acombination thereof in transceiver module 123 shown in FIG. 5 result insignificant negative gain slope, then equalizers 510-1 and/or 510-2 canbe set to establish corresponding positive gain slope compensation(i.e., setting the switches 515 to couple the inductor 511 to theamplifier 514 in parallel). Because of the additive nature offrequency-dependent gain, the resulting frequency-dependent gain of thetwo devices when coupled to one another will be a frequency-dependentgain that includes the sum of the two corresponding individualfrequency-dependent gains. Accordingly, when two devices with oppositelysigned gain slope (e.g., one device having positive gain slope and onedevice having negative gain slope) are coupled to one another, thefrequency-dependent gain of the two devices can be flatter than thefrequency-dependent gain of either device independently.

FIG. 8 is a graph 800 of one example scenario in which thefrequency-dependent gain of a particular variable equalizer 510 can beset to compensate for the composite negative gain slope of thefrequency-dependent gain profile 300 of a particular device or circuitto which it is coupled. In one scenario, the frequency-dependent gainprofile 300 corresponds to the frequency-dependent gain of a particulardevice or circuit (e.g. the transceiver module 123) illustrated in FIG.3. In some embodiments, to correctly set the compensatingfrequency-dependent gain of the variable equalizer 510, it is necessaryto first measure the frequency-dependent gain of the circuit or devicethat needs to be compensated.

The frequency-dependent gain profile 300 can be determined by measuringthe gain 801 response to signals in the frequency spectrum 802. In oneembodiment, the frequency-dependent gain profile 300 can be measuredmanually by a technician who passes signals at various frequenciesthrough the device. In other embodiments, the frequency-dependent gainprofile 300 can be measured by a computer system more quickly byautomatically passing signals at all frequencies through a device andmeasuring the gain. Manually or automatically measuring the gain of aparticular circuit or device may include comparing the amplitude (e.g.,power, voltage, current, etc.) of an input signal to the amplitude ofthe output signal. One of ordinary skill in the art will recognize thereare many ways to measure and/or calculate gain of a circuit.

In various embodiments, gain is a measure of the ability of a circuit toincrease the power or amplitude of a signal from the input to theoutput, by adding energy to the signal from some power source. Gain canbe defined as the mean ratio of the signal output of a circuit or deviceto the signal input of the same circuit or device. Gain is oftenexpressed using logarithmic decibel (dB) units. A gain greater than 1(i.e., >0 dB) is indicative of amplification. Amplification is typicallyachieved using an active component or circuit. In contrast most passivecircuits will have a gain less than 1. In various embodiments of thepresent disclosure, the term gain refers to power gain.

The power gain may be calculated according to the following equation(where P_out is the power of the output signal and P_in is the power ofthe input signal):

In decimal logarithm notation:

Gain=10 log(P_out/P_in)dB;

Gain can also be calculated using natural logarithm notation:

Gain=ln(P_out/P_in)Np

with result in units known as nepers (Np) instead of decibels (dB).

In embodiments of the present disclosure, any calculation of power,voltage, or current gain can be used without departing from the spiritor scope of the invention. Once the gain values for signals spanningsome portion of the frequency spectrum are determined for a particularcircuit or device, the gain values can be plotted as a function offrequency to generate a corresponding frequency-dependent gain profile.In the example shown, the frequency-dependent gain profile 300 indicatesthat the circuit or device includes gain values ranging from an upperlimit at 310 and a lower limit at 305 corresponding to a range of gainvalues of L dB 315. The range of L dB 315 may be too wide to allow thecircuit or device to effectively process signals without having toincrease the dynamic range with which the circuit or device is operated.For example, signals in the lower end of the frequency spectrum 802 maybe amplified to the point that the modulated signal is clipped by theupper limit of the dynamic range. On the opposite end of thefrequency-dependent gain profile 300, signals in the upper end of thefrequency spectrum 802 may be attenuated to the point that they are lostin the noise of the circuit or device. Various embodiments of thepresent disclosure advantageously provide for the variable compensationof systematic frequency-dependent gain to allow various circuits anddevices to operate with improved power consumption characteristics andsignal-to-noise ratio performance by reducing the range of gain in theassociated frequency-dependent gain profile.

Establishing Frequency-Dependent Gain Compensation

FIG. 8 illustrates the ability of a variable equalizer 510 to reduce therange of frequency-dependent gain of a given device or circuit. In theparticular example shown, the original frequency-dependent gain of thedevice or circuit is illustrated by the aforementionedfrequency-dependent gain profile 300. Since the frequency-dependent gainprofile 300 has significant negative gain slope, the variable equalizer510 can be set to establish a frequency-dependent gain with some levelof positive gain slope. In particular, the frequency-dependent gain ofthe variable equalizer 510 may be represented by the frequency-dependentgain profile 630. The gain profile 630 includes gain values ranging from633 to 637 spanning a range of P dB 635. As illustrated, P is less thanL. Accordingly, when the variable equalizer 510 is coupled to theparticular device or circuit, the corresponding frequency-dependentgains are additive. The resulting frequency-dependent gain is thecomposite of the frequency-dependent gains of the device or circuit andthe variable equalizer 510, represented in FIG. 8 as the compositefrequency-dependent gain profile 803.

While the composite frequency-dependent gain profile 803 is notperfectly flat and includes negative gain slope with gain values rangingfrom levels indicated by references 805 to 810, the range 815 of gainvalues is improved over the uncompensated frequency-dependent gainprofile 800. Some embodiments of the present invention are directedtoward flattening the frequency-dependent gain of a given device orcircuit, and not necessarily achieving zero gain slope or ripple. Forexample, establishing frequency-dependent gain with gain values rangesfrom approximately 2 dB to 10 dB may be sufficient for transmitting andreceiving microwave and radio frequency electronic signals for satelliteand terrestrial point-to-point communication with improved powerconsumption characteristics.

Adjusting various types of electronic devices, such as TRIA 120, to havesufficiently flat frequency-dependent gain has traditionally beenaccomplished by manually adjusting the frequency-dependent gain ofindividual circuits and components. Essentially, a technician wouldmanually determine and calculate the frequency-dependent gain of thedevice as a whole or on the component circuit level. Given a particularfrequency-dependent gain profile with various degrees of gain slopeand/or ripple, the technician would begin adding components in anattempt to flatten out the frequency-dependent gain profile. However,because adding compensation circuitry to one component usually causesthe frequency-dependent gain of another component to change, thetechnician would need to iteratively check and adjust thefrequency-dependent gain of each component and the device as a whole. Inlarge scale devices with many components that can contribute to thefrequency-dependent gain of the device, manually finding and attemptingto compensate for sources of significant gain slope and ripple can be anarduous and time consuming endeavor. Embodiments of the presentinvention allow for improved devices, systems, and methods for fast andcost effective frequency-dependent gain compensation in various widebandwidth systems. Such embodiments are advantageous in large-scaleproduction when even small delays in completing the assembly ofindividual units can aggregate into significant delays in completing aquantity of units.

FIG. 9 illustrates an example system 900 for establishing variablefrequency-dependent gain compensation using a variable equalizer 510,according to embodiments of the present disclosure. In one embodiment,the system 900 may include a device, such as TRIA 120, configured withone or more variable equalizers 510. The TRIA 120 may also include anumber of other components, such as signal processing circuits ordevices. The TRIA 120 may include a microcontroller 921 and the signalprocessing circuits may be a radio frequency/microwave transceivermodule ASIC 925, also referred to herein as the transceiver module 925.The microcontroller 921 may be coupled to the transceiver module 925 tosend signals to its various components. Accordingly, the signalprocessor 927, the variable equalizer 510, and/or the control circuitcan include input terminals for receiving signals from themicrocontroller or other external source.

The transceiver module 925 may incorporate functionality forestablishing transmission paths and receive paths for bidirectionalcommunication between a computing device in one location and a networkservice via an access point in another location. In some embodiments,the transceiver module 925 may be implemented as a monolithic integratedcircuit device, or MMIC.

The transceiver module 925 may include one or more signal processingcircuits 927. Signal processing circuits 927 may process a signal toamplify, attenuate, convert the frequency, or otherwise modify thesignal. The transceiver module 925 may also include a control circuit923. The control circuit 923 may receive signals on an input terminalfrom an external source, such as the microcontroller 921, or accesspredetermined settings stored in a memory or register. The controlcircuit 923 may then establish control signals in response to thesignals received from the external source or the predetermined. In theparticular example shown, the predetermined gain compensation settingscan be stored in the control circuit 923 in register 929. While theregister 929 is illustrated as being part of the control circuit 923,one of ordinary skill in the art will recognize that the gaincompensation settings may also be stored elsewhere in the system 900.For example, the gain compensation settings can be stored in memoryseparate from the control circuit 923, and provided to the controlcircuit 923 on its input terminal as signals by the microcontroller 921.

In one embodiment, one or more variable equalizers 510 and one or morecontrol circuit 923 can be implemented in a unitary integrated circuit(IC) for establishing frequency-dependent gain. As such, in oneembodiment, a variable equalizer 510 can be implemented in an IC thatincludes a corresponding control circuit 923. In some embodiments, thecontrol circuits 923 of the IC can be used to control the multiplevariable equalizers 510 according to signals received on one or moreinput terminals of the control circuit 923 or the IC. In someembodiment, the control circuits 923 of the IC can control multiplevariable equalizers 510 of the IC according to predetermined gaincompensation settings stored in register 929.

While the signal processing circuit 927 is illustrated having only asingle path, one of ordinary skill in the art will recognize that signalprocessing circuit 927 may include multiple paths processing signals.For example, one path (e.g., a transmit path) may include one or morevariable equalizers 510 and one or more control circuits 923, whileanother path (e.g., a receive path) may include one or more othervariable equalizers 510 and one or more other control circuits 923.

In one embodiment, the TRIA 120 may operate independently according tocomputer readable code including instructions for operatingmicrocontroller 921 and/or the transceiver module 125 to transmit andreceive electromagnetic signals to facilitate communication between anindoor unit 110 and a remote device. In other embodiments, the TRIA 120may be operated by the processor 910 in an external computing device(e.g., a desktop computer, a dedicated testing device, or a portablecomputing device, etc.).

To determine the gain compensation settings for variable equalizer 510to establish the best type and level of gain compensation, the processor910 can send control signals to the microcontroller 921 according tocomputer readable code that includes instructions for running a testroutine to establish or characterize the frequency-dependent gain of thetransceiver module 925 and/or the TRIA 120 as a whole. For example, theprocessor 910 can send signals to the microcontroller 921 to generateand/or send test signals at various frequencies through the componentsof the TRIA 120 including, but not limited to, the transceiver module925. In addition, the processor 910 can be coupled to the output of theTRIA 120 and/or the outputs of the transceiver module 925, through oneor more intermediate circuits or devices, to measure and/or calculatethe respective frequency-dependent gains of the TRIA 120 and/ortransceiver module 925. Based on the determined frequency-dependent gainand the available levels and type of frequency-dependent gaincompensation that the variable equalizer 510 can establish, theprocessor 910 can determine the settings for the variable equalizer 510to establish a composite frequency-dependent gain to be within a targetrange of gain values (e.g., within a range of 2 dB).

In one embodiment, the variable equalizer 510 can be designed andmanufactured in one of variety of configurations to establish differenttypes and different degrees of variable frequency-dependent gain.Accordingly, a variable equalizer 510 can be selected based on the typeand degree of frequency-dependent gain of the circuit or device to whichit will be coupled.

In one embodiment, the configuration of the variable equalizer 510 mayprovide for establishing positive and/or negative gain slopecompensation. In addition, the configuration of the variable equalizer510 may provide for establishing gain slope of various degrees. Forexample, the variable equalizer 510 can include selectable componentsfor establishing positive or negative gain slopes (e.g., −1, −2, +1, and+2, or any other values of gain slope) that may be useful forcompensating for the frequency-dependent gain slope of a particularsignal processing circuit or device. For example, if the determinedfrequency-dependent gain of the TRIA 120 or the transceiver module 925is determined to include typical gain slope of approximately ±2, then aparticular variety of variable equalizer 510 that can establish a gainslope of ±2 can be chosen to be included in the TRIA 120. In oneembodiment, the gain slope values are determined by inductance valuesand capacitance values selected for the inductors, capacitors, andresistors in the variable equalizer 510.

In another embodiment, the variable configuration of the variableequalizer 510 may provide for establishing higher orderfrequency-dependent gain compensation types, such as ripple. Forexample, a variable equalizer can be configured to establish gain rippleof various shapes and amplitudes. The amplitude, period, and frequencylocations of the zero slopes in the gain ripple can be variable. Othervariable equalizers can be configured to establish frequency-dependentgain compensation profiles that include positive and/or negative gainslope with varying magnitudes of slope and gain ripple of various shapesand amplitudes.

In one embodiment, the variable equalizer 510 can include selectablecircuits and/or components for establishing various patterns andamplitudes of ripple-type frequency-dependent gain compensation. Inaddition, the variable equalizer 510 may include settings for shiftingthe frequency-dependent gain up or down the frequency spectrum so thatthe frequency-dependent gain profiles of the circuit or device ofinterest and the variable equalizer 510 intersect in a frequency rangeof interest. In one embodiment, the variable equalizer 510 may includeamplifiers, resistors, and/or active gain compensation circuits that canbe selected by corresponding switches to shift the correspondingfrequency-dependent gain along the frequency spectrum or boost theoverall gain.

In various embodiments, the configuration settings of the variableequalizer 510 can be set by signals from an external source, such as themicrocontroller 921, processor 910, and the like. Once the settings forthe variable equalizer 510 that establish appropriatefrequency-dependent gain compensation is determined, the settings can bestored to a memory or register. Thus, when the TRIA 120 or thetransceiver module 925 is activated, the control circuit 923 canconfigure the variable equalizer 510 according to the gain compensationsettings. As shown, the gain compensation settings can be stored in aregister 925 control circuit 923.

FIG. 10 is a schematic diagram of an example circuit 1000 according toan embodiment of the present disclosure. Circuit 1000 can includefunctionality for a combined signal control and transceiver integratedcircuit that incorporates one or more variable equalizer circuits 510with signal processing circuits 1011, 1012, and 1013 and control circuit1040. The circuit 1000 can be used in various bi-directionalcommunication systems. Accordingly, the circuit 1000 can include atransmit path 1010 and a receive path 1020 for processing transmissionsignals from a local device or system and signal received from a remotesource. As previously discussed herein, such embodiments can beimplemented in and improve various point-to-point terrestrialcommunication systems (e.g., microwave band data links and Internetaccess) and satellite-based communications (e.g., bent pipe Internetaccess).

In one embodiment, the transmission path 1010 can include an inputterminal 1001 and an output terminal 1002, as well as multiple variableequalizers 510, multiple variable attenuators 1011, one or moreamplifiers 1012 and/or signal mixers 1013 coupled to one another. In theexample shown, the variable equalizers 510 are disposed at the beginningof the transmission path 1010 (i.e., near the input terminal), howeverthe variable equalizers 510 may be located anywhere within thetransmission path 1010 without deviating from the spirit or scope of thepresent disclosure.

In one embodiment, the receive path 1020 can include an input terminal1003 and an output terminal 1005, as well as multiple variableequalizer's 510, multiple variable attenuators 1011, one or moreamplifiers 1012 and/or signal mixers 1013 coupled to one another. Thereceive path 1020 can include circuitry for receiving both right-handedand left-handed polarized RF receive signals. In one embodiment, thereceive path 1020 includes a single path that can be shared with signalsof multiple polarization using a receive polarization switch 1014.

In an embodiment, the frequency-dependent gain of the variableequalizers 510 can be set using the predetermined gain compensationsettings 1007 stored in the register 1041 of the control circuit 1040.The predetermined setting 1007 can be determined by various methodologydescribed herein. In another embodiment, the frequency-dependent gain ofthe variable equalizers 510 can be set by an external source, such as amicrocontroller or microprocessor (not shown). In either embodiment, thefrequency-dependent gain of the variable equalizers 510 can be set bycontrol signals 1008 routed to the variable equalizer 510. (e.g.,Rx_Slope 1008-1 and Tx_Slope 1008-2). The control signals 1008 can beprovided to the variable equalizers 510 by the control circuit 1040based on the settings in the register 1041 or signals received from theexternal source.

Embodiments in which the register 1041 sends the control signals 1008are useful in scenarios in which the type and degree of necessaryfrequency-dependent gain compensation for the circuit 1000, and/orattached devices, has already been determined. Thus, when circuit 1000is activated, the frequency-dependent gain of the variable equalizers510 will be set according the predetermined gain compensation settings1007 to establish the desired or acceptable level of gain slope orripple for the circuit 1000.

Embodiments in which the control circuit 1040 establishes controlsignals 1008 in response to an external source are useful fordetermining the settings for the required or desired types and levels offrequency-dependent gain for each variable equalizer 510. In suchembodiments, an external source, such as a testing or characterizationcomputer system can feed test signals of various frequencies across theavailable frequency spectrum into the circuit 1000, and/or the devicesto which it is coupled, and measure the frequency-dependent gain. Theexternal source can then send signals that the control circuit can useto establish control signals 1008 that iteratively change the settingsof the variable equalizers 510, and measure the compositefrequency-dependent gain of the circuit 1000 with the various settings.The external source can then automatically choose or recommend the bestpossible settings for the variable equalizers 510 based on the variouscomposite frequency-dependent gains and a set of target gaincharacteristics for the desired or tolerable compositefrequency-dependent gain. In one embodiment, the external source can tryevery possible setting combination of the variable equalizers 510,compare the corresponding composite frequency-dependent gains, and thendetermine the optimal or most desirable variable equalizer settingcombination based on the comparison. The settings can then be stored inthe register 1041. While testing all possible variable equalizer settingcombination may take some finite amount of time, it can lead to the bestresult because all possible composite frequency-dependent gain profilescan be evaluated relative to the target gain characteristics.

However, in high-volume production, even marginal amounts of time perunit can compound into significant aggregate delays. Adding even anextra second of time per unit in a one million unit order can cause adelay of more than 11 days. Accordingly, in some embodiments, to savetime, the external source may be set to try one particular set ofsetting for the variable equalizers 510 and determine the correspondingfrequency-dependent gain. For example, a manufacturer may determine thatmost devices with the circuit 1000 require +2 gain slope compensation,so the external source can begin with sending signals to the controlcircuit to set the variable equalizers 510 to establish a +2 gain slope.To ensure that the frequency-dependent gain of the particular circuit1000, or the device to which circuit 1000 is coupled, is best improvedby the +2 gain slope compensation, the external source can then bracketthe initial settings to some predetermined number of settings thatresult in frequency-dependent gain above and below that established bythe initial settings. For example, in addition to measuring thefrequency-dependent gain at settings that establish +2 gain slope, theexternal source can also measure the frequency-dependent gain forsettings that establish +1 and +3 gain slope. From the limited selectionof settings, the external source can then determine which of the threepossible composite frequency-dependent gains is the best and store thecorresponding settings in the register 1041. Depending on the number ofpossible settings for variable equalizers 510 and the number units to betested/characterized, the time savings afforded by testing the circuit1000 with a limited number of settings can be significant when comparedto testing the circuit 1000 with all possible settings.

FIG. 11 is a flowchart of a method 1100 for determining the gaincompensation settings of a variable equalizer 510 to establishfrequency-dependent gain compensation for a system or device to which itis coupled. The frequency-dependent gain compensation can be based on aset of target characteristics for the desired or tolerable compositefrequency-dependent gain. For example, the target characteristics caninclude definitions of the desired flatness of the compositefrequency-dependent gain in the transmit path and/or the receive path.Such definitions can include specifications for the maximum range ofgains values for the composite frequency-dependent gain profile and/ormaximum magnitudes of gain slope. While the flowchart in FIG. 11references measuring the frequency-dependent gain of a transceiver, oneof ordinary skill in the art will recognize that the method can be usedto determine the settings for one or more variable equalizers 510 toestablish frequency-dependent gain compensation in any type of device orcircuit with any number of signal paths.

In one embodiment, the method can begin at action 1110 in which acomputing device measures the initial frequency-dependent gain of one ormore signal paths in a transceiver with a set of initial gaincompensation settings. In one embodiment, the initial gain compensationsettings can refer to the default settings of a particular variableequalizer 510. The default gain compensation settings in some variableequalizers 510 can establish no gain at all. (i.e., a frequencyindependent bypass). However, the default settings for other variableequalizers 510 can establish a base level of frequency-dependent gainthat includes some level of gain slope or ripple. The default settingsfor yet other variable equalizers 510 can establish a base level of gainindependent of frequency (i.e., zero gain slope or ripple). Measuringthe initial frequency-dependent gain of the transceiver can includesending signals with known signal levels at various frequencies spanninga particular frequency band through the transceiver and measuring thesignal levels of the output signals. The gain for each frequency canthen be calculated by comparing the signal levels of the input signalsagainst the signal levels of the output signals. As described herein,the gains can be calculated and described in units of decibels ornepers. In one embodiment, the gain for each frequency can then beplotted to generate a frequency-dependent gain profile for the compositefrequency-dependent gain of the transceiver and/or the variableequalizer 510. For example, the gain can be plotted as a decibels vsfrequency.

Once the frequency-dependent gain of the transceiver and the variableequalizer 510 with the initial gain compensation settings is known, thecomputing device can determine gain compensation that would most likelyadjust the frequency-dependent gain of the transceiver toward the targetcharacteristics, in action 1120. In one embodiment, determining the gaincompensation can include analyzing the frequency-dependent gain profileof the transceiver to calculate how much the profile needs to beflattened. In another embodiment, determining initial gain compensationcan include analyzing the frequency-dependent gain profile of thetransceiver to calculate where there are ripples in the gain profile.Based on the analysis of the frequency-dependent gain profile of thetransceiver and/or the variable equalizer 510, the computing device candetermine and set the gain compensation settings for the variableequalizer 510, in action 1130.

In some embodiments, determining the gain compensation settings caninclude referencing specifications for one or more particular variableequalizers 510 to determine the possible levels of frequency-dependentgain compensation that the equalizers 510 can establish. Based on thespecifications for the particular variable equalizers 510, the computingdevice can determine the corresponding settings necessary to establishone or more of the possible levels of frequency-dependent gaincompensation. Once the settings are determined, the computing device,either directly or through a microcontroller or control circuit, can setthe gain compensation settings of the variable equalizers 510 accordingto the determined gain compensation settings.

In action 1140, the computing device can repeat the process formeasuring the frequency-dependent gain of the transceiver and thevariable equalize 510 configured according to the determined gaincompensation settings. As described above, the computing device can sendinput signals of a known signal level at various frequencies through thetransceiver and the variable equalizer 510, and compare the outputsignals with the input signals. In some embodiments, measuring thefrequency-dependent gain of the transceiver with frequency-dependentgain compensation can include generating a frequency-dependent gaincompensation profile.

In action 1150, the computing device can compare the compensatedfrequency-dependent gain with the frequency-dependent gain with thedefault gain compensation settings. Based on the comparison, thecomputing device can determine whether the frequency dependence of thegain has been improved in determination 1153. Determining whether thefrequency-dependent of the gain has been improved may include analyzingthe magnitude of the gain slope and/or the range of gains of thefrequency-dependent gain profile. Accordingly, improvements in thefrequency dependence of the gain profile may include determining areduction in the range of gains (e.g., 10 dB to 5 dB) or a reduction inthe magnitude of the gain slope. If no improvement is detected or if thefrequency-dependence of the gain profile worsens (i.e., the magnitude ofthe gain slope or the range of gains increases), then the computingdevice can change the sign of the gain compensation, in action 1155.Changing the sign of the gain compensation can include referencingspecifications for the variable equalizer 510 to determine the settingsfor establishing frequency-dependent gain that compensates in theopposite direction of the previously attempted gain compensationsettings. For example, if the previously attempted settings for thevariable equalizer establish a positive gain slope of a given magnitude,then changing the sign of the gain compensation may include selectingsettings for the variable equalizer 510 that establish a positive gainslope of a smaller magnitude or a negative gain slope. Based on thechange of sign of gain compensation, the computing device can reset thegain compensation settings based on the determined change in sign ofgain compensation, in action 1130. At this point, actions 1130 through1153 can be repeated to evaluate the efficacy of various gaincompensation settings, until at determination 1153 the computing devicedetermines that there has been an improvement in frequency-dependentgain.

In action 1157, the computing device can determine whether there aremore gain compensation settings available for the variable equalizer510. If there are more gain compensation settings available, then thecomputing device can change the gain compensation setting of thevariable equalizer 510 to one of the remaining gain compensationsettings, in action 1160. In action 1130, the computing device can thenset the gain compensation settings according to the next gaincompensation settings and repeat actions 1140 through 1157 until noadditional gain compensation settings remain untested.

In action 1170, the computing device can then determine the best gaincompensation settings by comparing the previously generatedfrequency-dependent gain profiles of the transceiver and variableequalizer 510 with the various gain compensation settings. In someembodiments, comparing the frequency-dependent gain profiles can includeanalyzing the magnitude of the gain slope and/or the range of the gains.In one embodiment, the computing device may determine that the best gaincompensation settings as the settings that correspond to thefrequency-dependent gain profile with the smallest gain range and/or thesmallest magnitude of gain slope. In other embodiments, determining thebest gain compensation settings may include identifying the settingsthat correspond to the frequency-dependent gain profile closest to thetarget characteristics.

In action 1180, the computing device can store the best gaincompensation settings in a register or other memory in the transceiver.

FIG. 12 illustrates an example computing device and networks that mayuse or be used to implement embodiments of the present disclosure.Computing device 1210 includes a bus 1205 or other communicationmechanism for communicating information, and a processor 910 coupledwith bus 1205 for processing information. Computing device 1210 alsoincludes a memory 1202 coupled to bus 1205 for storing information andinstructions to be executed by processor 910, including instructions forperforming the techniques described above. This memory may also be usedfor storing temporary variables or other intermediate information duringexecution of instructions to be executed by processor 910. Possibleimplementations of this memory may be, but are not limited to, randomaccess memory (RAM), read only memory (ROM), or both. A storage device1203 is also provided for storing information and instructions. Theinformation instructions can be in the form of computer readable codestored on the storage device, accessible and executable by processor toimplement various techniques and methods of the present disclosure.Common forms of storage devices include non-transitory, non-volatilecomputer readable media, for example, a hard drive, a magnetic disk, anoptical disk, a CD, a DVD, a flash memory, a USB memory card, or anyother medium from which a computer can read.

Computing device 1210 may be coupled via the same or differentinformation bus, such as bus 1205, to a user interface device 1212, suchas a touchscreen, a liquid crystal display (LCD), and LED display, andthe like, for displaying information and accepting user input. Amicrocontroller 921 or microcontroller interface is coupled to the bus1205 for communicating control signals from the processor 910 to one ormore variable equalizer 510. The combination of these components allowsthe user to communicate with the system and the system to communicatewith a circuit or device that includes a variable equalizer 510.

Computing device 1210 also includes a network interface 1204 coupledwith bus 1205. Network interface 1204 may provide two-way datacommunication between computing device 1210 and the local network 1220.The network interface 1204 may be a local area network (LAN) card toprovide a data communication connection to a compatible LAN. The LANcard may include a wireless LAN (WLAN) card for communicating with acorresponding wireless network. In any such implementation, networkinterface 1204 sends and receives signals that carry digital datastreams representing various types of information.

Computing device 1210 can send and receive information, includingmessages or other interface actions, through the network interface 1204to an Intranet or the Internet 1230. In some embodiments, the networkinterface 1204 and/or the local network 1220 can communicate with system100 of FIG. 1 to send and receive signals with any of servers. Forexample, communication between computing device 1210 and any of theservers 1215, and 1231 to 1235 can be accomplished using one or moreinstances of system 100. The same instances of system 100 may also beused for communication between any two servers 1231 to 1235.

The above description illustrates various embodiments of the presentdisclosure along with examples of how aspects of the present disclosuremay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present disclosure as defined by thefollowing claims. Based on the above disclosure and the followingclaims, other arrangements, embodiments, implementations and equivalentswill be evident to those skilled in the art and may be employed withoutdeparting from the spirit and scope of the invention as defined by theclaims.

What is claimed is:
 1. A circuit comprising: a variable gaincompensation circuit to establish a variable frequency-dependent gain;and a control circuit comprising an input terminal and coupled to thevariable gain compensation circuit, wherein the control circuit isconfigured to control the variable frequency-dependent gain of thevariable gain compensation circuit in response to a signal received onthe input terminal from an external source.
 2. The circuit of claim 1,wherein the control circuit further comprises a register, and whereinthe control circuit establishes a control signal to control the variablefrequency-dependent gain of the variable gain compensation circuit inaccordance with a predetermined setting stored in the register.
 3. Thecircuit of claim 1, wherein the variable gain compensation circuitcomprises a plurality of N variable gain compensation devices toestablish a plurality of N corresponding component variablefrequency-dependent gains, and wherein the variable frequency-dependentgain of the variable gain compensation circuit is a composite of atleast some of the plurality of N component variable frequency-dependentgains.
 4. The circuit of claim 3, wherein the plurality of N variablegain compensation devices are the same and the corresponding pluralityof N component variable frequency-dependent gains are approximatelyequal to each other.
 5. The circuit of claim 3, wherein at least one ofthe plurality of N variable gain compensation devices is different fromat least one other of the plurality of N variable gain compensationdevices, and wherein at least one of the corresponding plurality of Ncomponent variable frequency-dependent gains is different from at leastone other of the plurality of N component variable frequency-dependentgains.
 6. The circuit of claim 3, wherein the plurality of N variablegain compensation devices each comprise: an inductor; a capacitor; aresistor; and an amplifier; wherein each of the inductor, the capacitor,and the resistor is selectively coupled to the amplifier in parallelthrough one or more corresponding switches.
 7. The circuit of claim 1,wherein the variable frequency-dependent gain comprises a gain slope. 8.The circuit of claim 1, wherein the variable frequency-dependent gaincomprises a gain ripple.
 9. The circuit of claim 1, wherein the variablegain compensation circuit comprises a plurality of M possibleconfigurations to establish a plurality of M corresponding discretefrequency-dependent gains.
 10. The circuit of claim 1, wherein thecircuit is a monolithic microwave integrated circuit (MMIC).
 11. Atransceiver circuit comprising: a transmit path comprising a firstvariable gain compensation circuit to establish a variablefrequency-dependent transmit gain; a receive path comprising a secondvariable gain compensation circuit to establish a variablefrequency-dependent receive gain; and a control circuit comprising aninput terminal coupled to the first variable gain compensation circuitand the second variable gain compensation circuit, wherein the controlcircuit is configured to control the variable frequency-dependenttransmit gain of the first variable gain compensation circuit and thevariable frequency-dependent receive gain of the second variable gaincompensation circuit in response to a signal received on the inputterminal from an external source.
 12. The transceiver circuit of claim11, wherein the transmit path comprises a first plurality of signalprocessing devices, wherein the variable frequency-dependent transmitgain of the first variable gain compensation circuit is set in responseto a first frequency-dependent gain of the first plurality of signalprocessing devices, wherein the receive path comprises a secondplurality of signal processing devices, and wherein the variablefrequency-dependent receive gain of the second variable gaincompensation circuit is set in response to a second frequency-dependentgain of the second plurality of signal processing devices.
 13. Thetransceiver circuit of claim 11, wherein the control circuit comprises aregister, and wherein the control circuit establishes one or morecontrol signals to control the variable frequency-dependent transmitgain of the first variable gain compensation circuit and the variablefrequency-dependent receive gain of the second variable gaincompensation circuit in accordance with a predetermined setting storedin the register.
 14. The transceiver circuit of claim 11, wherein thevariable frequency-dependent transmit gain of the first variable gaincompensation circuit is set to establish substantially flatfrequency-dependent gain through the transmit path, and wherein thevariable frequency-dependent receive gain of the second variable gaincompensation circuit is set to establish substantially flatfrequency-dependent gain through the receive path.
 15. The transceivercircuit of claim 14, wherein the substantially flat frequency-dependentgain through the transmit path corresponds to a reduction in a dynamicrange of power output of the transmit path.
 16. A method of equalizingfrequency-dependent gains in an integrated circuit, the methodcomprising: providing a plurality of signal processing devices; defininga transmit path through a first subset of the plurality of signalprocessing devices; defining a receive path through a second subset ofthe plurality of signal processing devices; coupling a first variablegain compensation circuit to the transmit path; and coupling a secondvariable gain compensation circuit to the receive path.
 17. The methodof claim 16, further comprising fabricating the integrated circuit. 18.The method of claim 16, further comprising: determining a firstfrequency-dependent gain through the transmit path; determining a secondfrequency-dependent gain through the receive path; configuring the firstvariable gain compensation circuit in response to the firstfrequency-dependent gain of the transmit path to establish acompensating frequency-dependent transmit gain; and configuring thesecond variable gain compensation circuit in response to the secondfrequency-dependent gain of the receive path to establish a compensatingfrequency-dependent receive gain.
 19. The method of claim 18, wherein:configuring the first variable gain compensation circuit comprisesselecting one of a plurality of M discrete settings for the firstvariable gain compensation circuit; and configuring the second variablegain compensation circuit comprises selecting one of a plurality of Ndiscrete settings for the second variable gain compensation circuit. 20.The method of claim 19, further comprising: providing a register; andstoring the one of the plurality of M discrete settings and the one ofthe plurality of N discrete settings in the register.